The invention relates to a control head for rotary filters with adjustable filtrate zones.
Known control heads in rotary filters, for instance as described in EP 0 400 787, (U.S. Pat. No. 5,053,123) have the recurring problem of bubbles forming and air being discharged, causing the water column formed in the dropleg to break and consequently the vacuum formed to break as well. As a result, there is no more dewatering action. There have been attempts, for instance in WO 94/12261, at shaping the control head such as to collect the bubbles at one point. This did not yield the desired effect, however, because time and again, larger groups of bubbles were entrained, with the resulting above-described effect.
It is the objective of the invention to reduce the flow resistance in the control head.
This is achieved by providing at least one filtrate separator, which is furnished with means to deflect the flow. On account of the deflection of flow provided, the filtrate can advantageously be routed to the droplegs without hitting against a surface and thus causing bubbles to form by the vortex created.
A further development of the invention is characterized by the fact that at least one deflector is foreseen for diverting the flow, advantageously with several deflectors being foreseen in a parallel arrangement. Thus, flow deflection is achieved especially efficiently and by simple means.
One advantageous development of the invention is characterized by the fact that the filtrate separate runs in a deflector plate which is fixed in the casing. With such an arrangement, the flow is completely diverted whatever the position of the filtrate separator. One advantageous development of the invention is characterized by the fact that the channels formed by the means of flow deflection run into channels formed in the casing between fixed guiding plates. Thus, the filtrate flowing from the control head can be especially well deflected to the filtrate pipes, whereby flow losses are minimized.